This invention relates to a combinatorial weighing method and apparatus and, more particularly, to a combinatorial weighing method and apparatus for conveying a plurality of buckets by means of a conveyor, each bucket carrying a quantity of articles to be weighed, finding the weight of the articles in each bucket, and discharging from selected buckets those articles which, in combination, give a total weight equal or closest to a preset target weight, which combination of articles is referred to as the "best" combination.
It is often required to weigh out highly accurate quantities of articles that vary in weight from one to another. Examples of such articles are vegetables and fruits, confectioneries, perishables, fabricated articles, etc. When weighing out quantities of lettuce, for example, wide disparities in weight can be noticed from one head to another. In order to weigh such articles it is general practice to make use of a combinatorial weighing apparatus (computer scale) that relies upon a computer.
A combinatorial weighing apparatus is adapted to weigh articles automatically by measuring the weights of articles which have been introduced into a plurality of weighing hoppers, selecting the combination of articles whose total weight is equal or closest to a preset target weight, discharging the selected articles from the weighing hoppers which contain them, and then replenishing these hoppers with articles to prepare for the next weighing cycle. Repeating these operations provides batches of the articles, each batch having a total weight equal or closest to the target weight.
Reference will be had to FIG. 1 to describe the structure and operation of a conventional computer scale. Reference numeral 11 denotes a main feeder of vibratory conveyance type. Articles to be weighed are introduced into the main feeder 11 and imparted with vibratory motion so as to be dispersed radially outward from the center of the main feeder. Numerals 12, 12, . . . denote n-number of weighing stations which are arranged around the main feeder 11 along radially extending lines to receive the articles dispersed by the main feeder. Each weighing station 12 includes a dispersing feeder 12a, a holding vessel 12b, a holding vessel gate 12c, a weighing hopper 12d, a weight sensor 12e, and a weighing hopper gate 12f. The dispersing feeder 12a comprises an independently vibratable conveyance device for feeding the articles by means of vibration, or an independently operable shutter device for delivering the articles in batches. In either case, each dispersing feeder 12a is so arranged that the articles received from the centrally located main feeder 11 can be introduced into the corresponding holding vessel 12 b disposed therebelow. The holding vessel gate 12c is provided on each holding vessel 12b in such a manner that the articles received in the holding vessel are released into the weighing hopper 12d when the gate 12c is opened. Each weight sensor 12e is attached to the corresponding weighing hopper 12d and is operable to measure the weight of the articles introduced into the weighing hopper. The weight sensor 12e is adapted to supply a combination computing unit with an electrical signal indicative of the measured weight. The combination computing unit then selects the best combination of articles that gives a total weight closest to a preset target weight. Each of the weighing hopper gates 12f is provided on the corresponding weighing hopper 12d. The combination control unit, upon receiving the signals from each of the weight sensors 12e, responds by opening the weighing hopper gates 12f only of those weighing hoppers 12d that will give the best combination of articles, as mentioned above. The articles from the weighing hoppers 12d selected in this manner fall through the open weighing hopper gates and are discharged into a common collecting chute 13 where they are collected together. The collecting chute 13 has the shape of a funnel and is so arranged as to receive the articles from any of the circularly arrayed weighing hoppers 12d via the hopper gates, which are located above the funnel substantially along its outer rim. The articles received by the collecting chute 13 are collected at the centrally located lower end thereof by falling under their own weight or by being forcibly shifted along the inclined wall of the funnel by a mechanical scraper or the like, which is not shown. The collecting chute 13 is provided with a timing hopper 14 at the lower end thereof for temporarily holding the collected articles. The arrival of an externally applied signal from a packing device or the like causes the timing hopper 14 to release the retained articles from the weighing apparatus, namely from collecting chute 13 which constitutes the lowermost stage of the apparatus, to a separate item of equipment, such as the packing device.
The operation of the above arrangement will now be described in greater detail. At the beginning the holding vessels 12b and weighing hoppers 12d contain a supply of the articles. The weight sensors 12e associated with the respective weighing hoppers 12d measure the weight of the articles in each hopper and produce weight values L.sub.1 through L.sub.10 which are sent to the combination computing unit. The computing unit performs an arithmetic combination computing operation using the weight values L.sub.1 through L.sub.10 and selects the combination of articles that gives a total weight closest to the set target weight. A drive control unit (not shown) opens the weighing hopper gates 12f which are selected on the basis of the best combination, whereby the selected weighing hoppers discharge their articles into the collection chute 13. This will leave the selected weighing hoppers 12d empty. Now the holding vessel gates 12c of those holding vessels 12b corresponding to the empty weighing hoppers 12d are opened to introduce a fresh supply of the articles into said weighing hoppers, leaving said holding vessels empty. Next, the dispersing feeders 12a which correspond to the empty holding vessels 12b are vibrated for a predetermined period of time to deliver a fresh supply of the articles to said holding vessels. This restores the weighing apparatus to the initial state to permit resumption of the computing operation for selecting the best weight combinations in the manner described. Automatic weighing by the combinatorial scale proceeds in continuous fashion by repeating the foregoing steps.
Articles which can be dealt with effectively with the combinatorial weighing apparatus of FIG. 1 are limited to bulky, easily separable items such as fruits, vegetables and confectioneries, which can be dispersed and transferred from one part of the weighing apparatus to another because of their ability to move freely. Products such as raw meat tend to adhere to one another and to the equipment and, hence, cannot be handled by the conventional combinatorial weighing apparatus.